The yoga teacher

Does my bum look big in this?" laughs 71-year-old Pam Horton, down on all fours, her back to the camera in preparation for a headstand. She raises her legs up, then asks: "What's next?" as the photographer asks her to pull pose after pose - camel, cobra, tree, and general superwoman-style stretching of legs, straight in front, up in the air, and behind the head.

Of course we expect yoga teachers to be supple, even at Horton's age - after all, isn't lifelong flexibility the promise of the practice? But what is remarkable is her stamina; she spends three hours on the photoshoot, moving through the postures with few objections, much humour and some sensible boundaries - she doesn't want to be photographed in positions displaying parts of her that, as she puts it, "no one wants to see in a woman of my age".

Date of birth aside, Horton is something of a teenager among older people, and says "70 isn't really old these days". Although she lives in sheltered accommodation with her 76-year-old wind-surfing husband in a village outside Carlisle (they moved in 20 years ago when they had to nurse Horton's mother), many of her neighbours are in their 90s, and she's seen the life expectancy of those around her rise over the past two decades.

It's a shock to hear her remember that the smog was once so bad in Manchester that conductors walked in front of buses with torches - she doesn't look old enough. Her youthful image is part yoga and part modern dress - today she's wearing an Armani T-shirt and she likes to shop in TK Maxx. "People are surprised when they find out my age," she says, "although not when they learn what I do." She's taught yoga (all styles) since she was 35 - today she holds five classes a week for 20- to 80-year-olds at a leisure centre in Carlisle and teaches people long distance, using tools on her up-to-date website (which offers free downloads).

"Yoga can have a tremendous effect on you, whatever age you start," she says, "but I find I don't need to do much practice to keep supple, as my awareness of my body posture has become second nature over the years." She reveals that yoga has a more meaningful message, too. "I'm aware of the fragility of health and that it can change without warning. So I always retain a sense of detachment - I'm not pleased with myself if I do a complicated yoga pose, I'm pleased for myself. You've never got life cracked. Yoga teaches you that."